The invention relates to a method of driving a display device comprising a ferro-electric liquid crystalline medium between two supporting plates, the first plate comprising a system of row electrodes and the second plate comprising a system of column electrodes defining display elements at the area of the crossings of row and column electrodes, said display elements reaching a desired transmission state from an extreme transmission state during selection.
Such a method is suitable for driving passive matrices having large numbers of lines. Since the contrast is maintained, the method is very suitable for LCD-TV.
A method of the type mentioned in the opening paragraph is described in EP 0,214,857. In the method described in EP 0214857 the desired transmission states (grey scales) are obtained in that, dependent on the desired transmission value, a display element is switched on in n successive rasters during a weighted period. This implies that a picture memory is necessary and the ferro-electric liquid crystalline medium must switch n times as fast, notably in video uses. Moreover, the display element is never switched on completely during the second and subsequent selected rasters, which leads to loss of brightness.